The present invention relates to an apparatus for generating a waveform data read signal to be supplied to a memory for storing waveform data of a musical tone.
Recently, main circuits of electronic musical instruments have been constituted by digital circuits. When a tone signal is to be generated in accordance with digital signal processing, one-period waveform data of a tone produced by a natural musical instrument is prestored in a memory, and the stored data is read out in response to a waveform data read clock which has a frequency corresponding to the frequency of the tone to be generated. In this conventional waveform data read clock generating circuit, a generator is arranged to generate a 4-bit note code signal in accordance with a depressed key of the keyboard. The generated note code signal is supplied as an address signal to a ROM so as to determine a pitch of a given note. The ROM stores pitch data each having a predetermined value corresponding to a frequency of the given note. The pitch data read out from the ROM is supplied to a subtractor which comprises a full-adder. The subtractor performs subtraction for a number of times corresponding to the frequency. When the outputs from the full-adder become all "0", the waveform signal read clock generating circuit generates a signal of logic "1". This "1" signal is supplied as the waveform signal read clock to a waveform memory, so that one sampled peak value date is read out. Therefore, the higher the pitch of the note corresponding to a depressed key, the shorter the period of time taken for setting the outputs from the full-adder to be all "0". The duration for reading out the peak value data from the waveform memory is thus shortened. Thus, the resultant note has a high pitch.
In general, a one-octave scale consists of 12 notes. Four-bit data must be used to generate 12 different note codes. In this sense, the ROM for storing pitch data must have 12 memory locations, and 6-bit pitch data must be stored in each memory location. Therefore, this ROM must have a relatively large memory capacity, resulting in high cost of an electronic musical instrument.